The present disclosure relates to motorized and non-motorized cycles having variable geometry cycle frames, and particularly to an apparatus for adjusting the length, height, and/or angle of a cycle frame component.
Motorized and non-motorized cycles, such as motorcycles, bicycles, and three-wheelers (collectively “cycles”) typically have a welded frame that includes a “gooseneck” and one or more downtubes and one or more backbones (referred to respectively in the singular herein, although more than one member may comprise each). The gooseneck, also known as a steering head, typically includes a segment of tubing that is supported by the backbone and downtube. Additionally, the gooseneck typically pivotably supports the front wheel assembly, generally referred to as a fork. The backbone is typically coupled to an upper portion of the gooseneck and typically extends rearward to the seat pan, for example supporting the seat and fuel tank. The downtube is typically coupled to a lower portion of the gooseneck and typically extends downward, for example in front of the engine, and couples with the motor mount. The backbone and downtube typically each have a fixed length.
The rake angle of a cycle is defined as the angle of the steering axis of the front wheel fork relative to an imaginary vertical axis, typically 30 degrees in production cycles. The wheel base of a cycle is defined as the distance between the front and rear wheel axles. The gooseneck height of a cycle is defined as the vertical distance from the road surface to the gooseneck. A combination of the rake angle and gooseneck height contribute to the determination of the wheelbase. A combination of the rake angle, gooseneck height, and wheelbase further contribute to the determination of the style of the cycle and its stability and handling characteristics. For example, a low rider/pro-street style chopper typically has a shorter gooseneck height, smaller rake angle, and shorter wheelbase than that of a tall boy style chopper. A desired combination of frame characteristics may be selected for particular driving conditions or handling performance. For example, a lower gooseneck height and a longer wheel base provide for higher stability such as is desirable for highway driving. Alternatively, a higher gooseneck height and a shorter wheel base provides for more aggressive turning response, for example for city driving.
The rake angle and gooseneck height are determined at least in part by the relative downtube “rise” length and backbone “stretch” length; therefore, to provide a particular rake angle and gooseneck height combination, the characteristics of specific downtube and backbone lengths may be desirable at certain times, while other downtube and backbone lengths may be desirable during different circumstances, for example, depending on driving conditions and rider preference. For example, variations in rider preference make it desirable for a chopper motorcycle to be adjustable from a low rider/pro-street style configuration to a tall boy style configuration. Adjustment of the downtube and backbone lengths can also provide adjustment of the cycle to better accommodate various sizes of riders.
Typically motorcycles have a fixed frame geometry, i.e., the length for the backbone, length for the downtube, wheel base length, gooseneck height, and rake angle. Some motorcycles, known as choppers, are modified with a fixed stretch to the backbone length, fixed rise to the downtube length, and fixed increase in the rake angle. Thus, typical choppers have an altered, but fixed, frame geometry.
Some prior configurations for have allowed for the adjustment of the rake angle but have not allowed for adjustment of the length of both the downtube and backbone, thereby independently varying the rake angle and gooseneck height. In addition, while prior configurations have altered a stock style motorcycle to a chopper, they do not allow one type of chopper to be changed to another type of chopper, for example, from a low rider/pro-street style chopper to a tall boy style chopper. Additionally, while some prior configurations have used pneumatic systems for adjusting the rake angle, with pneumatically operated rake angle adjustment, a loss of air pressure can cause the cycle to “nose-dive,” causing an unsafe condition that can lead to an accident.